Magnetic Resonance Imaging (MRI) is widely accepted as an aid to the medical diagnosis of patients, for example, to detect bone fractures and tumors. MRI is "non-invasive" in that it does not require a surgical procedure, such as a biopsy, to examine the patient's tissues. In many circumstances it produces superior images compared to X-rays, including CT (Computerized Tomography) scanning, and without any side-effect physiological danger from repeated X-ray dosages.
However, the images produced of soft "moving" organs, i.e., organs which normally are in motion, have proven difficult to interpret due to the large amount of "noise" (non-information). For example, a person may breathe (inhale and exhale) 10-20 times a minute with his diaphragm and lungs almost constantly moving. An MRI image of a "slice" (a two-dimensional image reconstruction of a two-dimensional body cross-section) may take one or two minutes. Using fast NMR scan techniques, for example, using a smaller flip angle on some pulses, may still require many milliseconds, for example, 200 milliseconds, to produce a single slice. The resulting image may be blurred or difficult to read. An analogy would be taking a photograph, using a slow shutter speed, for example, 1/60th seconds, of a rapidly moving object, resulting in a blurred image.
To speed up the taking of the MRI image would help reduce the noise arising from moving body organs, i.e., body artifacts. However, generally, the faster the image is taken, the less information it contains. The use of fast MRI imaging of the diaphragm is discussed in Gierada D. S. et al, "Diaphragmatic motion: fast gradient recalled echo MR imaging in healthy subjects," Radiology 194, 879-884, 1995.